MDCAT Biology: Nervous and Chemical Coordination

Comprehensive practice flashcards covering muscle structure, nervous system anatomy, nerve impulses, human brain regions, nervous disorders, and the endocrine system based on MDCAT lecture notes.

Epimysium

The outermost layer of connective tissue that wraps the entire skeletal muscle.

Perimysium

The connective tissue that wraps around a fascicle, which is a bundle of muscle fibers.

Endomysium

The connective tissue located between individual muscle fibers.

Chemoreceptors

Receptors responsible for detecting smell, taste, and blood levels of $CO_2$, oxygen, glucose, amino acids, and fatty acids.

Mechanoreceptors

Receptors that detect stimuli of touch, pressure, hearing, and equilibrium.

Photoreceptors

Electromagnetic receptors that respond to light stimuli, such as rods and cones in the eyes.

Nociceptors

Undifferentiated nerve endings that produce the sensation of pain.

Meissner's Corpuscles

Encapsulated neuron endings acting as touch receptors, located in the papillae of fingertip ridges.

Pacinian Corpuscles

Encapsulated neuron endings present deep in the body that receive deep pressure stimuli and detect vibrations.

Neuroglia

Cells that play a vital role in the nutrition of neurons and their protection by the myelin sheath, making up half of the nervous system in higher animals.

Nissl's granules

Groups of ribosomes associated with rough E.R. and Golgi apparatus found in the cell body of a neuron.

Dendrites

Protoplasmic processes that carry nerve impulses towards the cell body of a neuron.

Axons

Protoplasmic processes that conduct impulses away from the cell body and may be more than a meter long in some neurons.

Resting Membrane Potential

The charge difference across the membrane of a non-conducting neuron, approximately $-70\,mV$, with the inside being more negative than the outside.

Active Membrane Potential

The state where $Na^+$ rushes in and the inner membrane becomes more positive ($0.05\,\text{volts}$ or $-50\,mv$) for about a millisecond.

Saltatory impulse

A nerve impulse in myelinated neurons that jumps from one node of Ranvier to another.

Synapse

Microscopic gaps between the axon endings of one neuron and the dendrites of the next, where no cytoplasmic connection exists.

Neurotransmitters

Chemical messengers such as acetylcholine, adrenaline, nor-epinephrine, serotonin, and dopamine released at axon endings to transmit messages across a synapse.

Meninges

A triple layer beneath the cranium and vertebral column that protects the brain and spinal cord.

Cerebrospinal fluid (CSF)

A fluid similar in composition to blood plasma that bathes the CNS, cushions against jolts, and fills the ventricles of the brain and central canal of the spinal cord.

Thalamus

A relay center in the forebrain that carries sensory information from visual, auditory, and skin pathways to the limbic system and cerebrum.

Amygdala

A cluster of neurons in the limbic system involved in producing sensations of pleasure, punishment, love, hate, fear, rage, and sexual arousal.

Hippocampus

A region of the limbic system required for learning and the formation of long-term memory.

Hypothalamus

A coordination center between the nervous and endocrine systems that regulates body temperature, thirst, hunger, and controls pituitary hormone release.

Corpus Callosum

A large band of axons that allows communication between the left and right cerebral hemispheres.

Reticular formation

A part of the midbrain/hindbrain that screens input information before it reaches higher brain centers.

Pons

A structure above the medulla involved in the rate and pattern of breathing and the transition between sleep and wakefulness.

Cerebellum

The part of the hindbrain that coordinates body movements, maintains body position, and is highly developed in birds for flight.

Ganglia

Concentrations of the cell bodies of neurons located in the peripheral nervous system.

Somatic Nervous System

The part of the motor nervous system that controls voluntary movements of skeletal muscles under conscious control.

Sympathetic System

A division of the autonomic nervous system associated with fight or flight responses, such as increasing heart rate and dilating pupils.

Parasympathetic System

A division of the autonomic nervous system associated with the relaxed state, promoting digestion and retarding heart rate.

Parkinson's Disease

A progressive nervous disorder characterized by involuntary tremors, rigidity, and poor balance, caused by the death of cells in the basal ganglia.

Epilepsy

A convulsive disorder characterized by sudden alterations in brain function associated with excessive rapid electric discharge in the gray matter.

Alzheimer’s disease

First described in 1907, a disease causing decline in brain function and dementia, potentially linked to genetic predisposition or high aluminum levels.

Hormone

Organic compounds secreted by endocrine glands and transported by blood that regulate enzymatic reactions and metabolic activities in target tissues.

Somatotrophin (STH)

A growth hormone from the anterior pituitary; excess in early life leads to Gigantism, while under-secretion leads to Dwarfism.

Luteinising Hormone (LH)

A gonadotrophic hormone that stimulates ovulation and formation of the corpus luteum in females, and testosterone production in males.

Antidiuretic Hormone (ADH)

Also called vasopressin, it increases water reabsorption in the kidneys; its lack produces Diabetes insipidus.

Oxytocin

A hormone from the posterior pituitary that stimulates uterine contractions during childbirth and milk ejection from mammary glands.

Thyroxin

An iodine-containing amino acid hormone that stimulates the breakdown of glucose, release of heat, and the basal metabolic rate.

Myxoedema

A condition in adults resulting from iodine deficiency characterized by a swollen neck (goiter), increased weight, and reduced metabolic rate.

Calcitonin

A thyroid hormone that prevents the removal of $Ca^{++}$ ions from bones when blood calcium levels are high.

Parathormone

A hormone from the parathyroid glands that raises blood calcium levels; under-activity causes muscular tetany.

Insulin

A protein hormone produced by $\beta$-cells of the pancreas that lowers blood glucose levels by increasing glycogen synthesis and cell utilization.

Diabetes Mellitus

A condition resulting from a failure to produce insulin, characterized by high blood sugar, sugar in the urine, and dehydration.

Glucagon

A peptide hormone produced by $\alpha$-cells of the pancreas that increases blood glucose levels by promoting glycogen breakdown.

Aldosterone

A mineralocorticoid steroid from the adrenal cortex that conserves $Na^+$ ions by preventing loss through kidney tubules.

Cushing’s disease

A disorder caused by over-secretion of cortical hormones, leading to excessive protein breakdown and muscular/bone weakness.

Gastrin

A hormone produced by the mucosa of the stomach's pyloric region that stimulates gastric juice secretion.

Progesterone

Produced by the corpus luteum, it inhibits FSH secretion, thickens the uterine wall, and maintains pregnancy.

Feedback Mechanism

An interaction where a controlling mechanism is itself controlled by the products of the reactions it regulates.